CGA to VGA Converter

Hardware questions and modifications

CGA to VGA Converter

Postby mcsew2k » Wed Jan 25, 2012 2:02 am

Instead of buying a replacement PCjr Color Display, I was considering using an arcade CGA-to-VGA convertor such as this one:

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 0806675555

Does anyone have any experience with using one of these convertors with the PCjr? I am told that it cannot handle the Intensity bit for 16-color CGA. I am wondering if it can be modified; is anyone knowledgeable about such things?
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Re: CGA to VGA Converter

Postby jmetal88 » Wed Jan 25, 2012 12:12 pm

Yeah, there are instructions on the 'net somewhere for converting digital RGBI to analog RGB, but I can't remember where.

You'll notice that instead of the orangey-brown, you'll now have dark yellow, though, IIRC.
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Re: CGA to VGA Converter

Postby jharre » Fri Aug 16, 2013 9:32 am

Sorry to revive an old thread, but is anybody using some sort of adapter to use a VGA flat-panel display with their machine? The ebay link in the first message is dead now, but maybe it was similar to this: http://www.ebay.com/itm/Arcade-Game-RGB-CGA-EGA-YUV-to-VGA-Video-Converter-HD-/330605923350?pt=LH_DefaultDomain_0&hash=item4cf9a60c16

I'm primarily interested in 80 column text mode and fear that these CGA to VGA adapter boards would produce a lot of "smear". For 30 bucks, guess it isn't too expensive of a gamble. But it would be nice to hear if there is something that works well.

Richard at Computer-Reset tells me that there was a VGA (sidecar?) for the PCjr at one time, but "it didn't work very well", whatever that means.

Jim
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Re: CGA to VGA Converter

Postby James » Fri Aug 16, 2013 11:54 am

You can find a Digital CGA > VGA adapter but they are very expensive. You can find CGA LCD monitors but they are also pricey. The one below is an example. I don't know how well it works with the PCjr.

http://www.provantage.com/future-busine ... RCL02X.htm

The PC Enterprises Display Master was a VGA sidecar adapter for the PCjr. It required a motherboard mod, which is one of the five systemboard modifications they offered. My PCjr is modified so if anyone ever sees one of those please let me know

James
-PCjr (1989)-DOS 3.3, Racore Drive II, jrIDE-128 MB DOM, jrExcellerator, Tandy Mod, Serial Card, Combo v2, Config Plus, IBM Parallel Port, Megaboard, Xircom PE3-10BT
-PCjr (2001)-DOS 3.3, jrIDE-128 MB DOM, NEC v20, Parallel Port, Comswap, Xircom PE3-10BT
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Re: CGA to VGA Converter

Postby Brutman » Sat Aug 17, 2013 5:03 pm

Jim,

I have a monitor for you but it is going to be a few weeks before I can ship it.
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Re: CGA to VGA Converter

Postby PNKlett » Tue Aug 20, 2013 3:41 pm

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Re: CGA to VGA Converter

Postby mcsew2k » Tue Aug 20, 2013 5:57 pm

Hi Paul,

I have no experience with that unit, but I can see from the wiring diagram that it does not have an input for the "intensity" signal of the PCjr monitor output. IBM CGA is not just RGB, but is RGBI, so to say. I have not seen one of these convertors that have that feature.

David
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Re: CGA to VGA Converter

Postby jharre » Thu Aug 22, 2013 3:06 pm

Paul -

That CGA -> VGA converter looked pretty interesting until I got to the bottom of the page and saw it is $90 plus $10 for the cable, plus shipping. That's an awful lot just to play around. :o Have you tried one in text mode?

Jim
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Re: CGA to VGA Converter

Postby jmetal88 » Thu Aug 22, 2013 10:11 pm

I'd like to take a shot at designing a CGA (RGBi) to VGA converter someday. Don't know if I have the knowledge yet, but it'd be fun to mess around with.
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